The Hive

Should Cities Install Moving Sidewalks?

An idea for urban transport, cribbed from the airport.

Are moving walkways viable for urban transportation?

In this project, “ Nimble Cities,” Slate wants to hear your best ideas for making urban transportation more efficient, safe, and pleasant. Read Tom Vanderbilt’s explanation of Nimble Cities. You can scan all the proposals submitted by readers so far here and vote for your favorites. Tom Vanderbilt will evaluate the most interesting ideas and the top vote-getters.

While the last two Nimble Cities ideas I’ve written about—reforming parking codes and creating bicycle highways—have been fairly sober and down to earth, that’s not to say there’s not room for the dreamers, and I couldn’t help but notice among the proposals several that included some form of urban moving walkway. One reader called for an “electrorheological (ER) ‘smart fluid’ to create flexible moving walkways” while another suggested tapping into the power of “crazy circular motion” to move people around. (He proposed building a series of concentric moving walkways.) “The station itself is a fixed hub. From where you stand you can see many concentric circles of moving walkway stretching into the distance. The one nearest you is moving at .5 miles per hour. You step onto it. Boom. The next is moving at 1 mile per hour. You step onto it. Boom.” And so on.

If it sounds like the stuff of science fiction … well, it has been. In his short story “The Roads Must Roll,” Robert Heinlein imagined the United States—facing a war-strained petroleum shortage that meant the “end of the automobile era was in sight”—shifting to a series of massive commuter moving walkways. Of the first “mechanized road,” built between Cincinnati and Cleveland, Heinlein writes: “It was, as one would expect, comparatively primitive in design, being based on the ore belt conveyors of ten years earlier. The fastest strip moved only thirty miles per hour, and was quite narrow, for no one had thought of the possibility of locating retail trade on the strips themselves.”

The moving walkway, of course, is a firmly entrenched and familiar transportation technology, but it has been largely limited to controlled (and typically transportation-related) environments, like airports, train stations, or theme parks. Its history unspools further back than you might imagine. As Paul Collins has written, the first moving sidewalks were unveiled at Chicago’s 1893 Columbian Exposition (where they could shuttle 31,680 passengers per hour), again at the 1900 Paris Exhibition, and seemed well on their way to conquering cities like New York. As Collins writes, Max Schmidt, the creator of the Chicago walkway, “proposed a flurry of similar projects around Manhattan—running down Broadway, along Wall Street, over the Williamsburg Bridge and across 23rd and 34th Street. To Schmidt, the advantages of the moving walkway were so compelling that he was convinced they would supplant some subways rather than supplement them. By 1909, he was pushing a massive $70 million scheme that would provide Manhattan with a network of subterranean moving sidewalks.”

For a variety of reasons—maintenance concerns (think of how many escalators you’ve seen out of service), weather issues, and perhaps even that very competition with the subways—the moving walkways never took root in cities. After a half-century’s slumber they began to appear (under brand names like “Travelator” or “Speedwalk”) in places ranging from train stations to Disney’s Space Mountain, and even in cities like Tokyo (home to the Yebisu “Skywalk”) and Hong Kong, where one can find not only the world’s largest covered outdoor escalator, but three outdoor (and inclined) moving walkways.

But these instances hardly represent the future imagined by Max Schmidt or Robert Heinlein. For one, distances are short. For another, speeds are relatively slow; the American Society for Mechanical Engineers mandates a maximum speed of 4.57 meters per second, though for various reasons, including legal liability, that speed is rarely approached. Another problem is sheer ergonomics—the walkways have to ramp up to speed with minimal “upsetting effect.” As a study in the journal Transportation Research noted, “conventional moving walkways have a constant transport speed of approximately half of the maximum pedestrian walking speed. Their speed-range of 0.5–0.83 [meters per second] is considered low, sometimes resulting in a low level-of-service and passengers’ impatience.” This speed can be improved by actually walking on walkways, but many don’t seem to; Jerry Seinfeld singled out for opprobrium “the people who get onto the moving walkway and just stand there. Like it’s a ride. Excuse me, there’s no animated pirates or bears along the way here.”

And as at least one study (“Optimal speeds for walking and running, and walking on a moving walkway,” by Manoj Srinivasan, published in Chaos: An Interdisciplinary Journal for Nonlinear Science) has argued, moving walkways can actually result in lowered travel speeds versus normal walking, because of the congestion caused by people standing. (To counter this problem, the “pallet width” of moving walkways, as it known, has actually gotten wider, which allows walkers to pass people with luggage carts.) Even when one is alone on the belt and can walk without interruption, however, the time savings is on the order of a mere 11 seconds over a bit more than a football field’s worth of travel. There is also the larger question of whether we want to engineer yet another form of physical activity out of our lives.

Some have begun investigating so-called “accelerated moving walkways,” which would promise higher speeds (some three times conventional walkways) over longer distances. The speeds, in addition to the constantly available nature of moving walkways (eliminating wait time), would presumably offer benefits over other forms of transportation. But as was demonstrated by the case of the Trottoir Roulant Rapidethe higher-speed (11 kph) walkway installed in Paris’ Montparnasse station—the world doesn’t seem ready. (As Collins notes, it was troubled by design and maintenance issues and was taken out of service last year and converted into a regular walkway.)

The Trottoir Roulant was largely viewed as a boondoggle, but it was trying to meet a real need—one that will continue to be an issue for increasingly crowded cities—a need that the project’s manager described, in almost DeLillo-esque terms, to the BBC: “The real problem nowadays is how to move crowds,” he said. “They can travel fast over long distances with the TGV (high-speed train) or airplanes, but not over short distances (under 1 km).” In other words, in an age of mega projects and mass travel, the trek across the airport can take as long as the trip to the airport.

Read about how  eliminating parking spaces could improve urban transportation and how bicycle highways could increase cycling. View contest entries by clicking the button below.